Often used when something improves beyond expectations due to positive events or news. Their stock prices went through the roof after the merger was announced.
Pro Tip 2/3
Exaggeration
Can be used to exaggerate for dramatic effect, not always literal. When the celebrity entered, her fans' excitement went through the roof.
Pro Tip 3/3
Unexpected Spike
Describes a sudden and sharp increase, often surprising or unexpected. Demand for the new phone model went through the roof overnight.